They are the frail older couple, slumped in wheelchairs just behind the barriers on Tremont Street, hands entwined.

They are the police officers marching alongside, trying to keep their emotions in check as confetti rained down on them.

They are the father with his son on his shoulders, telling him that such things didn’t happen when he was a boy.

They are the young men screaming the lyrics to “Three Little Birds” and “Sweet Caroline.”

They are the fans of Boston, and on Saturday, hundreds of thousands of them came together for what has become a singular tradition in the Hub — the duck boat parade.

In the embarrassment of riches that has been the last 12 years of Boston sports, the “rolling rally” victory parade has become the ultimate fan experience, with no tickets and no disappointments, a guaranteed group smile in a city that could certainly use one.

They happen often, yes, but they never get old, for part of being a Boston fan is living with the feeling that this could be the last one. And so they came, to be with others like them, to bask in a sun that didn’t seem to care that it was Nov. 2, and to participate in that great regional religion that is the Boston Red Sox.

Yoon S. Byun/Globe Staff

The scene in Copley Square.

Arthur McDonough and his 9-year-old son, Tristan, got up early in Randolph, took the train in to Boston Common, and when the duck boats finally appeared and the wall of noise swept up Tremont Street, dad was covered in goose bumps.

“We’ve been talking a lot about how we’re sports buddies now,” McDonough said, “and when I tried to wake him up in the ninth inning the other night, he was back asleep in two seconds. But I told him we had to do this because you never knew when it might happen again. You have to experience it while it’s here. And when those duck boats finally appeared, I just kept saying to him, ‘Can you believe this? Can you believe this?’”

On the Esplanade, where fans lined “the banks of the river Charles” waiting for the duck boats to take their dip in that “dirty water,” Steve Hines of Cohasset had his 5-year-old son, Matthew, on his shoulders, so he could get a better look.

“They have three trophies,” Matthew noted as the World Series trophies were held aloft by the players on the boats. “They must be really good.” His father could only smile and offer his son a simple truth — you can’t take it for granted.

It was a day for celebration, for sure, but part of Saturday’s experience for many fans was one of simple thanks. They shook the hands of the police officers who escorted the duck boats, many of them the same men and women who ran toward the bombs in April.

And for many of those officers, fans themselves, there was a childlike thrill behind their cop facade. As the army of officers waited for the parade to begin, they were allowed to roam the grass at Fenway, to stand on the mound and kick up dirt on the warning track.

“I feel like someone’s about to come tackle me for being out here,” one officer said.

For most, the day began early, in the dark, with long commutes and tricky travel restrictions. By 6 a.m., the best front-row spots were taken along the route for the 10 a.m. parade, and at Fenway, the line for season ticket holders — who had been invited to come wish the duck boats off — snaked down Yawkey Way.

Marty Costello, a 64-year-old season ticket holder from Saugus, stood in the stands as the early-morning light peeked into the old ballpark. Already, he was overcome with the excitement, with the struggle to come up with any words that could possibly summarize this year.

“It’s surreal,” he said, as his wife and daughter stood with him. “I still can’t believe this happened, this year.”

As the Costellos waited for the players to appear, for the Dropkick Murphys to start playing, for another duck boat parade — another parade! — to begin, Marty held a simple homemade sign, one that many other fans stopped to photograph.

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